Test notes
CrossFire X presents a wealth of possible test configs, but we chose a couple that we thought would be representative of common configurations. For our quad-GPU tests, we used a pair of Radeon HD 3870 X2 cards, and for three GPUs, we used a single Radeon HD 3870 X2 paired with a Radeon HD 3870. Our test motherboard, a Gigabyte GA-X38-DQ6, has two PCIe x16 slots with a full 16 lanes of PCIe 2.0 connectivity routed to each. These hardware combinations should be more or less optimal for CrossFire X in terms of interconnect bandwidth and the like, giving it plenty of opportunity for performance scaling.

Please note that we tested the single and dual-GPU Radeon configs with the Catalyst 8.2 drivers, simply because we didn't have enough time to re-test everything with Cat 8.3. The one exception is Crysis, where we tested single- and dual-GPU Radeons with AMD's 8.451-2-080123a drivers, which include many of the same application-specific tweaks that the final Catalyst 8.3 drivers do.

Our testing methods
As ever, we did our best to deliver clean benchmark numbers. Tests were run at least three times, and the results were averaged.

Thanks to Corsair for providing us with memory for our testing. Their quality, service, and support are easily superior to no-name DIMMs.

Our test systems were powered by PC Power & Cooling Silencer 750W power supply units. The Silencer 750W was a runaway Editor's Choice winner in our epic 11-way power supply roundup, so it seemed like a fitting choice for our test rigs. Thanks to OCZ for providing these units for our use in testing.

Unless otherwise specified, image quality settings for the graphics cards were left at the control panel defaults. Vertical refresh sync (vsync) was disabled for all tests.